Apparatus for cold rolling threads



Jan. 19, 1954 TRlSHMAN 2,666,348

APPARATUS FOR COLD ROLLING THREADS Filed Dec. 16, 1950 Q 3 Sheets-Sheet l Jan. 19, 1954 1.. E. TRISHMAN 66 APPARATUS FOR COLD ROLLING THREADS Filed Dec. 16. 1950 's Sheets-Sheet 2 a 7- Toe/V5 7's.

Jan. 19, 1954 E. TRISHMAN 2,666,343

APPARATUS FOR COLD ROLLING THREADS Filed- Dec. 16, 1950 s Sheets-Sheet s IN V EN TOR. Lam/Emma TkISHMfiM w fm 5 a 7- roelv/s Y's.

Patented Jan. 19, 1954 ean UNITED STATES PATENT OFFICE APPARATUS FOR COLD ROLLING THREADS Lawrence E. Trishman, Beaver, Pa., assignor to The National Supply Company, Pittsburgh, Pa., a corporation of Pennsylvania Application December 16, 1950, Serial No. 201,163

5 Claims.

This invention relates to apparatus for cold working metals and, in particular, to apparatus for cold rolling tapered male threads.

As would be expected, the purpose of cold working threads is to harden their metal surfaces and thereby increase their fatigue resistance. In a number of cases tapered threads are used to couple together members which, in use, are subjected to great strains, and in such cases it is of utmost importance that the fatigue resistance of the threads be increased to a maximum. Thus, for example, it is extremely desirable that the tapered threads of oil well drill collars be hardened to a maximum fatigue resistance, because any fracture initiating at the thread requires the full length of the oil well pipe to be removed and the collar replaced.

There are devices for cold rolling threads, but, as far as I am aware, none of these are directed toward working tapered threads. To obtain maximum fatigue resistance, it is essential that the thread be cold worked a rather well-defined and limited amount which, if exceeded, starts minute cracks or tears in the metal structure that in use open up and eventually cause fractures, and this factor apparently has not been taken into consideration in these prior cold rolling devices. Stated in another manner, to obtain optimum fatigue resistance, it is essential that the working roll be capable of being so accurately controlled that minute adjustments of its working depth are possible,'and no apparatus for cold working tapered threads has been found that is capable of such control. Another deficiency of the known prior devices is that, for reasons which will be explained later, they work the threads in such a manner that the desired thread contour, normally formed by hobbing before the cold rolling, is distorted.

It is therefore among the objects of this invention to provide apparatus for cold working tapered male threads, the apparatus being of simple construction, sufficiently light to be manually assembled and operated in the field and being so arranged that the depth to which the metal of the threads is worked can be controlled accurately to minute fractional measurements.

A further object is to provide apparatus capable of functioning in such amanner without distorting the contour of the threads.

. According to the invention, the work-piece, which may be a drill collar, is securely held in a suitable frame, and the cold working members carried in another frame, this latter frameoeing adapted to receive the threaded end of the work-piece. The; cold working member is a work o .9: roll carried by and freely slidable along the sec 0nd. frame in a plane that is parallel to the taper of the thread of the work-piece. When the workpiece is inserted into the frame, the work roll is brought into contact with the thread and then is forced more deeply into the metal of the thread by roll-feeding means which, most suitably, includes a micrometer feed-screw that bears against a wedge member slidably mounted in the frame; the wedge providing the surface that is parallel to the taper of the thread. Rotation of the feed-screw operates to press the tapered surface of the wedge against the roll and thus move the roll radially of the work-piece into the desired cold-rolling engagement. This engagement being effected, cold rolling is performed by rotating either one, or both, of the frames, the rotation causing the roll to follow the thread and, since the roll must move along a plane that is parallel to the taper of the thread, there results a uniform and closely controlled rolling throughout the thread length.

Further, in the preferred form of the invention the work roll is so shaped that it engages only the root portion of the thread, the purpose of such an arrangement resulting from the fact that when both the roots and flanks of certain types of threads are engaged by the roll, the cold working causes excessive distortion of the contour of the thread, and, also, from my finding that the fatigue resistance of the thread is increased as much, if not more, when only the root is worked as when both the root and the flanks of the thread are worked.

Another feature utilized in the preferred form of the invention is a plurality of independently rotatable, back-up rolls mounted side-by-side on a common shaft and bearing against the crests of the thread. Such back-up rolls are used in place of a single solid, cone-shaped back-up roll which, as will be' more fully explained, would cause considerable undesirable slippage between itself and the work-piece.

The preferred embodiment of the invention is illustrated in the accompanying drawings of which Fig. 1 is a side elevation of the apparatus with certain portions shown in section to disclose underlying structure; Figs. 2 and 3 vertical sections along lines II-II and IIL-III, respectively, of Fig; 1; Fig. i a plan view of the feed screw mechanism for the work roll; Fig. 5 a diagram matic illustration of the manner in which the work roll engages the thread; and Fig. 6 a vertical section of a tool used to insure proper alignment of. the elements of the apparatus.

Referring to the drawings work-piece l, which is shown as an end portion of an oil well drill collar having a previously cut thread 2, is firmly clamped in a frame 3 that may be a conventional, rotatable lathe chuck, while the cold working tool and its associated mechanism are mounted in another frame 3 which, as shown, i adapted to receive the threaded end of the work-piece in an appropriate position for working its thread. Frame 4 is formed of front and rear opencentered, end plates 5 and 6 rigidly bolted together at their top and bottom portions, the top bolt mounting a bail by means of which frame 4 can be lifted and fitted around the work-piece. The functional elements for cold working the thread all are mounted in frame i and these, in general, include a work roll l mounted on a shaft 8 which, in turn, is supported in bearings formed in a roll carriage 9, the bottom surface of which is provided with a tongue il adapted to be received in a slot, or grooved track [2 formed on the upper surface of a wedge-shaped member l3. Also supported by frame 4 is a glide plate M on which wedge i3 is slidably mounted for 1onthread cone is lost.

gitudinal sliding movement with respect to the frame and, for purposes to be later described, wedge adjusting screws 85, are threaded into the base portion of both of th end plates so as to bear against the bottom surface of this glide plate It. Preferably, the work roll and its shafts both are formed of hardened steel and, if desired, suitable bronze wear pads may be secured to the bottom surface of the wedge, as well as to the portions of the carriag which slide on the upper fiat surface of the wedge.

Cold working of the threads is efiected by bringing work roll 1 onto cold rolling engagement with the thread, and then rotating chuck it, the chuck rotating the drill collar and thereby causing the work roll to follow and traverse the thread from one end to the other. It will be recalled, however, that the particular thread to be worked is tapered so that, as the roll traverses it, it must move radially away from it in a plane parallel to the taper in order to cold roll the thread uniformly. Accordingly, it is essential to this invention that track i2 of the wedge be sloped, or tapered, to the same degree as the taper of the thread so that the carriage may move down or up its tapered surface and maintain uniform rolling engagement with the thread.

Another feature of this invention is the provision of suitable back-up means for the work roll and, here again, the fact that the thread is tapered renders the specially-formed back-up means of this invention desirable. As best seen in Figs. 1 and 2, the back-up means includes a pair of truncated cone-shaped members I! each having its peripheral surface bearing against the crests of the thread and each being tapered, or inclined, to the same degree as the thread. Further, each of the cones is made up of a plurality of independently rotatable, disc-shaped rolls 18 mounted side-by-side on a common shaft I9 which is carried in end plates 5 and 6. Preferably, these rolls it each are provided with a narrow hub so as to space the rolls a minute distance one from the other to reduce frictional contact between them. Also, it is desirable to drill oil conduits 2G in shaft is so as to lubricate the rolls and further decrease frictional resistance to rotation.

The purpose of such a plurality of narrow backup rolls can best be understood if it be assumed that a solid, tapered roll were used in their place. Thus, if it be assumed that a solid roll were substituted, it will be appreciated that the pressure exerted by the work roll at the small end of the thread cone would tend to rotate the large end 5 the back-up roll at the same peripheral speed as the small end of the thread cone, but, at the same time, the small end of the back-up roll would rotate at a greater peripheral speed than the large end of the thread cone so that considerable slippage must occur at some point along these engaged surfaces. Such slippage, it has been found, causes the back-up rolls to crawl or feed toward the shoulder of the drill collar with the result that there is created a strong force tending to tilt the frame to such a degree that back-up roll contact at the large end of the Similarly, if the work roll were pressing against the large end of the thread cone, slippage between the small end of the thread cone and the large end of the back-up roll is produced with the result that back-up contact at the small end of the thread cone may be lost. However, by the use of a plurality of narrow backup rolls, such slippage is reduced to a minimum and, in fact, has been found to be practically negligible insofar as it is necessary to provide any clamping or bolting devices to offset the tilting force created by slippage.

As mentioned previously, one of the important features of this apparatus lies in its ability to cold roll a thread very accurately to minute fractions of an inch so that the cold rolling limitations set forth in my copending application, referred to above, can be met. Such accuracy is achieved by the use of the wedge and roll carriage arrangement and, in addition, by means of micrometer feed-screw mechanism, generally incheated by numeral 2|. The principal function of the feed screw mechanism is to feed, or press the roll into the metal of the thread to exactly the depth desired for the cold working, and, generally speaking, the mechanism includes a screw which indirectly bears against and is secured to the wedge so that as the screw is turned, the wedge is moved beneath the carriage to press the roll radially into the thread. As shown in Figs. 1 and 4, the feeding mechanism includes a threaded feed screw 22 on the outer end of which is mounted suitable micrometer adjusting mechanism so that the amount of the feed can be micrometrically determined, and the screw is meshed with a feed collar 23 which, as seen in Fig. 4, is yoke-shaped and is provided at its inner end with flanges that are bolted to frame plate 5. To secure the feed screw to the Wedge, the

inner end of the screw mounts a key 24' which closely fits into a socket formed in a small plate 25 that is secured to the wedge by screws 26. The purpose of securing the wedge to the feed screw is to permit th wedge to be drawn or pulled from beneath the work roll carriage, so that the work roll can part engagement with the thread.

In cold rolling with this apparatus, it also is necessary to assure that the work-piece is held in axial alignment with the backing rolls and with the working roll, as well as to insure that the backing rolls contact the crests of the thread. Further, it is equally important to assure that there is no lateral movement of the apparatus axially with respect to the threads or the drill collar shoulder, and for these purposes, a ring or collar 21 (Fig. 1) is bolted to the drill collar and engaged with the apparatus, the engagement being made by means of a flange 28 formed on collar 27 and locked in a groove formed in another half ring 29 which is bolted to plate 6 of aecama frame 4. The arrangement is such that. when halt ring 29 is engaged with collar 21,. the backingrolls bear against drill collar shoulder 30' and, also, contact the thread crests and lie in axial alignment with the work-piece roll. However, to effect such alignment, it first is necessary to accurately position ring 2'! with respect to drill collar shoulder 30, and. to do this, a special. tool, illustrated in Fig. 6 is provided.

- Referring to-Fig. G this tool includes an in.- ternally threaded ring 3 I provided with. handles 32: and recessed to receive a split ring 33 formed to: engage alignment ring 21? in the manner illustrated. Also, split ring 33 has a flat: wall 34 adapted to bear against the drill collar shoulder when the tool alignment ring if is in proper position with relation to this drill collar shoulder. To position ring 27, the elements are assembled in the manner illustrated in Fig- 6, and ring St is screwed onto the thread of the drill collar until shoulder 34 of split ring 33 engages the shoulder oi. the drill collar, and, when such engagement is effected, alignment ring 21' is secure'ly clamped to the drill collar by tightening the set screws in its periphery. The alignment ring being so positioned, threaded ring 3| is unscrewed permitting split ring 33 to be removed and, then, frame 4 of the cold rolling apparatus may be secured by dropping its'half ring 29 over the flange of alignment ring 21', it being understood that the alignment ring and the tool members are so dimensioned with respect to the other elements that when half ring 29' is engaged with the alignment ring, the backing rolls and the other members of the apparatus are in proper position for cold working.

The operation of the apparatus should be reasonably clear from the above description, but, to insure complete understanding, the manner in. whichthe apparatus is assembled as well as its operation will be reviewed. In the assemblage, the work-piece first is clamped in the lathe chuck and then alignment ring 21 secured to the work-piece by the aid of the alignment tool illustrated in Fig. 6. Frame 4 then is fitted over the threaded end of the work-piece and is engaged with alignment ring 2'! by means of its half ring 29. Such engagement being effected, it also is desirable to further support frame 4 to prevent its tilting laterally inone or the other direction. This may be accomplished by the use of a horizontal bar 31 bolted or otherwise secared to plate 6 and held in horizontal position by means of blocks 38 which rest on the ways of the lathe.

When frame 4 is fitted around the thread of the work-piece, work roll I is brought into initial contact with its thread. However, it is desirable that'the roll contact only the root of the thread since, as previously pointed out, any working of the flanks of the thread tends to distort the thread contour. For this purpose, the work roll is so shaped with respect to the thread that it can contact only the thread root and this condition is obtained by making the angle of divergence of the roll flanks less than that of the thread flanks, as is clearly illustrated in Fig. 5.

With the work roll engaging the root of the thread, the next step is to press the work roll into the root to a depth to which it is desired to cold work the metal. This is accomplished by rotating feed-screw 22 which presses the tapered surface of wedge i3 against the carriage and thereby moves the roll radially into the thread root. The proper engagement of the 6. work roll and. the thread having been so efiected, chuck 3 then is rotated in. one direction causing the roll to traverse the length of. the thread and then the lathe chuck: is rotated the opposite direction to return the work roll to its initial position.

Usually, steel threads shouldbe worked only to a. depth of approximately .010 inch because any appreciable. increase of this depth commences tears. and weak points in the metal of the thread. Using this .010 inch as an example, cold. rolling may be carried out first by advancing the work; roll into the thread root to a. depth of approximately .0025 inch and this minute fraction. may be measured by a suitable micrometer mounted. on the end of feed-screw 22. The thread then is cold. worked to this depth by rotating thev work-piece, following which. the micrometer screw is advanced another .0025 inch to feed the rolls. further into. the thread by that amount. This process: is continued until the de.-. sired cold. rolling depth, or a depth of approximately .01 inch, is achieved. By this means, very accurate control ofthe cold working possible and, it also will be noted that the work roll is positively and mechanically held in its cold rolling engagement with the thread so that occasional irregularities in the softness or; hardness in the metal of the thread will not afiect the accuracy of. the. cold working depth. Although. the apparatus is designed. for a. thread of a particular taper, it. is possible to vary to. some degree the taper of wedge [13.- so that the inclined plane through which the roll moves also will be varied. This adjustment is accomplished by previously described threaded screws [5 which project. upwardly" through the base of plates 4 and 6 and bear against glide plate IA of the wedge. It. is apparent that. adjustments made in one or the other of. these screws will change the inclination of the wedge.

In addition to the effectiveness of the apparatus, it should also be noted that its structure is relatively simple and inexpensive and that its parts are relatively lightso that the apparatus as, a whole can be handled easily by one or two men and, consequently, can be used in the field, or for example, in a shop at the site of an oil well.

According to the provisions of the patent statutes, I have explained the principle, preferred embodiment and mode of operation of my invention, and have illustrated and described what is now considered to represent its best embodiment. However, I desire to have it understood that, Within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

Iclaim:

1. Apparatus for cold rolling tapered male threads that have been formed on the ends of steel work-pieces, comprising a frame for engaging and firmly holding such a work-piece with its threaded end exposed, a second frame adapted to receive the exposed threaded end of the workpiece, means for effecting relative rotation between said frames, the second-named frame being provided with a rigid work-roll support lying in a plane parallel to the taper of the thread, a work roll rotatably borne by and freely slidable upon said support, and a back-up cone rigidly carried by said second frame for engaging the side of the work-piece opposite to said work roll, said cone comprising a plurality of freely rotatable idle rolls each having its thread-engaging surface tapered to conform to the taper of the thread on the work-piece, the rotation of one of said frames causing the work roll to follow the thread to cold work it whereby to increase its fatigue resistance.

2. Apparatus for cold rolling tapered male threads that have been formed on the ends of steel work-pieces, comprising a frame for engaging and firmly holding such a work-piece with its threaded end exposed, a second frame adapted to receive the exposed threaded end of the workpiece, means for effecting relative rotation between said frames, the second-named frame being provided with a rigid work-roll support lying in a plane parallel to the taper of the thread, a work roll carriage freely slidable upon said support and equipped with a rotatable thread-engaging work roll, and a back-up cone rigidl carried by said second frame for engaging the side of the Work-piece opposite to said work roll, said cone comprising a plurality of freely rotatable idle rolls laterally spaced from each other on a common axis, each idle roll having its thread engaging surface tapered to conform to the taper of the thread on the workpiece, the rotation of one of said frames causing the work roll to follow the thread and to slide said carriage upon its said support, whereby to cold roll the thread to increase its fatigue resistance.

3. Apparatus for cold rolling tapered male threads that have been formed on the ends of steel work-pieces, comprising a frame for engaging and firmly holding such a work-piece with its threaded end exposed, a second frame adapted to receive the exposed threaded end of the work-piece, means for effecting relative rotation between said frames, the second-named frame being provided with a rigid work-roll support a lying in a plane parallel to the taper of the thread, a work roll for engaging rotatably borne by and freely slidable upon said support, and at least two backup cones rigidly carried by said second frame for engaging the side of the workpiece opposite to said work roll, each of said cones comprising a plurality of freely rotatable idle rolls laterally spaced from each other on a common axis, each idle roll having its threadengaging surface tapered to conform to the taper of the thread on the work-piece, the rotation of one of said frames causing the work roll to follow the thread to cold roll it whereby to increase its fatigue resistance.

l. Apparatus for cold rolling tapered male threads that have been formed on the ends of steel work-pieces, comprising a frame for engag ing and firmly holding such a work-piece with its threaded end exposed, a second frame adapted to receive the exposed threaded end of the worktween said frames, the second-named frame being provided with a rigid work-roll support lying in a plane parallel to the taper of the thread, a work roll carriage freely slidable upon said support and equipped with a, rotatable thread-engaging work r011, means for adjusting said support radially of the Work-piece to position the work roll in rolling contact with th work-piece thread, and a back-up cone rigidly carried by said second frame for engaging the side of the Work-piece opposite to said Work roll, said cone comprising a plurality of freely rotatable idle rolls laterally spaced from each other on a common axis, each idle roll having its thread-engaging surface tapered to conform to the taper of the thread on the work-piece, the rotation of one of said frames causing the Work roll to follow the thread to cold roll it whereby to increase its fatigue resistance.

5. Apparatus for cold rolling tapered male threads that have been formed on the ends of steel work-pieces, comprising a rotatable chuck for engaging and firmly holding such a workpiece with its threaded end exposed, a frame secured in position around the exposed threaded end of the work-piece, said frame being provided with a rigid work-roll support lying in a plane parallel to the taper of the thread, a work roll carriage freely slidable upon said support and equipped with a rotatable thread-engaging work roll, means for adjusting said support radiall of the work-piece to position the work roll in contact with the Work-piece thread, and back-up cones rigidly carried by said second frame for engaging the side of the work-piece opposite to said work roll, each of said cones comprising a plurality of freely rotatable idle rolls laterally spaced from each other on a common axis, each idle roll having its thread-engaging surface tapered to conform to the taper of the thread on the work-piece, the rotation of one of said frames causing the work roll to follow the thread. and to slide said carriage upon its said support, whereby to cold roll the thread to increase its fatigue resistance.

LAWRENCE E. TRISHMAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 936,809 Pratt Oct. 12, 1909 1,045,093 Mark et a1. Nov. 19, 1912 1,188,461 McCain June 27, 1916 2,182,906 Unke Dec. 12, 1939 2,188,629 Giesey et al. Jan. 30, 1940 2,257,234 Gould Sept, 30, 1941 FOREIGN PATENTS Number Country Date 524,765 Germany July 10, 1928 

